1. Field of the Invention
This invention relates to a camera system in which by the mounting of a removably mountable lens, a plurality of electrical contacts between a camera body and the lens are brought into contact with one another and the transmission of a power source, signals, etc. is effected between the camera body and the lens.
2. Related Background Art
In a camera system according to the prior art, a circuit power source such as a DC--DC converter has been switched on by a switch operatively associated with the operation of an operating member such as a release button provided on the camera body side, whereby the electric circuit of the system has been operated.
In recent years, with an increase in the kinds of functions such as automatic focusing, power focusing and power zoom, various operating members and switches have come to be provided on the lens side as well, but in the system as described above wherein the power source is switched on by the switch on the body side, it is necessary to switch on the power source by the switch on the body side without omission and then operate the switch on the lens side in order to perform the operation of the lens side, and this has led to bad operability.
Also, in a camera system like the camera system disclosed in Japanese Laid-Open Patent Application No. 2-113229 wherein power supply is effected from a camera body to a motor contained in a lens to thereby effect driving, even if the lens side prepares a power supply demand signal for receiving the power supply for the motor, the demand signal cannot be put out because communication is not established in a state in which the electric circuit on the camera side is OFF. Therefore, when motor driving such as for power focusing is to be effected on the lens side, it has been necessary for the photographer to manually operate the switch on the camera body side without omission to thereby switch on the electric circuit and put out the power supply demand signal, and thereafter start power focusing or the like.
Now, U.S. Pat. No. 4,695,148 discloses the technique of switching on a power source on the camera body side from a flash device, and more specifically, there is a power source on the flash device side and an operating member on the flash device side is operated while that power source is switched on, whereby a power source on the camera body side is electrically switched on. Accordingly, when the power source on the flash device side is consumed up, the power source on the camera body side cannot be switched on from the flash device side.